Handheld medical reference application with integrated dosage calculator

ABSTRACT

A medical information device may include a general purpose computer such as a handheld computer, configured with a plurality of medical and drug information content pages and a reader application configured to display the medical and drug information content pages. To access the drug and medical information content pages, the reader may generate a plurality of parameter strings in response to user-selected medical and drug information. The medical information device may also include a drug dosing calculator application configured to receive at least one of the parameter strings generated by the reader application and to return dosing information to the reader application. The parameter string or strings may include drug dosing parameters corresponding to a user-selected medical condition and a user-selected drug and/or drug dosing parameters corresponding to medical and drug information included on a selected medical and drug information content page. The medical information device may also include a general medical calculator application configured to receive at least one of the parameter strings generated by the reader application and to return appropriate calculated results to the reader application.

BACKGROUND

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/442,538, filed Jan. 24, 2003.

[0002] This invention relates to medical information devices and methodsfor using medical information devices to assist in the diagnosis, care,and treatment of patients.

[0003] The amount of information that a healthcare professional musthave at his or her disposal to diagnose and treat patients can bedaunting. Healthcare professionals are overloaded with informationneeded to provide the best care for patients. Standards of care arerapidly changing for hundreds of medical conditions. There are thousandsof drugs each with unique side-effect profiles and tens of thousands ofdrug interactions, many of these potentially fatal. Dosages formedications must be calculated carefully, and may depend on thepatient's age, weight, body surface area, or other criteria. Also,dosages and/or calculation formulae may vary with the purpose of themedication (e.g., anesthesia or sedation), the condition being treated,and the method of administering the medication (e.g., oral orintravenous). Also, healthcare professionals may need to perform dozensof other medical related calculations a day, such as those relative tofluid and nutritional requirements, calculating electrolyte imbalances,and organ function metrics (e.g. cardiac output).

[0004] To provide effective care for a patient, today's healthcareprofessional needs a portable, comprehensive, integrated medical anddrug information resource that can instantly provide him or her withessential information and calculations at the bedside. The device shouldalso be capable of updating the medical and drug information.

SUMMARY

[0005] The PEPID medical reference application allows medicalprofessionals and non-professionals to accurately and quickly search formedical or drug reference information stored in PEPID content files onhandheld devices. A handheld device configured with the medicalreference application is referred to herein as a medical informationdevice. This product allows users to navigate through a hierarchicalrepresentation of medical and drug information on handheld devices andgain access to a variety of complementary applications. Thecomplementary applications include, for example, an integrated drugdosage calculator. While the benefits of the invention are most likelyto be achieved with the portability afforded by a handheld computer,such as a Palm OS or Windows Pocket PC device, the invention may also beimplemented on other computing devices, such as laptop and desktopcomputers.

[0006] A medical information device may include a general purposecomputer such as a handheld computer, configured with a plurality ofmedical and drug information content pages and a reader applicationconfigured to display the medical and drug information content pages. Toaccess the drug and medical information content pages, the reader maygenerate a plurality of parameter strings in response to user-selectedmedical and drug information. The medical information device may alsoinclude a drug dosing calculator application configured to receive atleast one of the parameter strings generated by the reader applicationand to return dosing information to the reader application. Theparameter string or strings may include drug dosing parameterscorresponding to a user-selected medical condition and a user-selecteddrug and/or drug dosing parameters corresponding to medical and druginformation included on a selected medical and drug information contentpage.

[0007] The medical information device may also include a documentmanager application, configured to receive the plurality of parameterstrings generated by the reader application and to provide medical anddrug information content pages to the reader application. The documentmanager application may be configured to manage an integrated medicaland drug information database, including updating and controlling accessto medical drug information content pages. The document managerapplication may be configured to allow access to medical druginformation content pages only during the time period of a usersubscription.

[0008] The medical information device may also include a unit conversioncalculator configured to receive at least one of the parameter stringsgenerated by the reader application and to return converted units to thereader application. The medical calculator device may also include ageneric calculator that is resident in the document manager applicationand is linked to calculator definition database and calculator lookuptables to provide calculator definitions.

[0009] A method for calculating drug dosing using a medical informationdevice may include the steps of configuring the computing device withmedical and drug information content pages and a drug dosing calculator,displaying at least one medical and drug information content page on thecomputing device, selecting a medical condition from a plurality ofmedical conditions displayed on the computing device based onobservations of a patient and displayed medical information, selecting adrug from a plurality of drugs displayed on the computing device,passing drug dosing parameters corresponding to the selected medicalcondition and the selected drug to the drug dosing calculator, anddisplaying a calculated drug dose. An additional step may includeselecting a method of administering the selected drug and wherein thedrug dosing parameters further includes parameters corresponding to theselected method of administering the drug.

DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a block diagram of a medical information devicecorresponding to an example of the present invention.

[0011]FIGS. 2a and 2 b comprise a table of examples of parameter stringsthat may be generated by the reader application.

[0012]FIG. 3 is a block diagram of a generic calculator corresponding toone aspect of the present invention.

DETAILED DESCRIPTION

[0013] 1 Medical Reference Application and Document Manager Application.

[0014] In an example illustrated in FIG. 1, a medical reference device10 comprises a sending application 12 associated with content files 20and further associated with a plurality of receiving applications bydefined links. The receiving applications may further be associated withone or more databases. In one example, the sending application 12 is adocument reader. The Reader may comprise an application configured toread hypertext mark-up language (HTML) or extensible markup language(XML) documents. In one example, the Reader may be an open-sourcebrowser. The receiving applications may include a Document ManagerApplication (DMA) 14 and one or more calculators, which may include unitconversion calculators 16 and drug dosing calculators 30. Also, the useof calculators in this document is not necessarily limited tomathematical calculations. A calculator as used herein may performnon-mathematical functions, such as drug interaction comparisons.

[0015] One feature of the PEPID medical reference device is a high levelof integration of a reader (sending application) 12 with an assortmentof complementary applications. The integration is achieved by providingthe capability to pass predefined data parameters 18between theapplications. The medical reference device has a standardizedapplication programming interface mechanism that enables it to easilyadd any number of integrations to complementary applications, includingan assortment of handheld medical calculators and a drug interactionreference. The integration is performed by defining links 18 between thesending application and the receiving applications. The Reader 12 may beconfigured to pass parameters to the receiving applications.

[0016] The Reader 12 may be associated with one or more content files20. Content files may be provided as a single file that includes aplurality of “reference cards”, or pages of information, provided in anencrypted handheld database or file store format. The reference cardsmay number in the hundreds or thousands. Multiple content files may alsobe accessed and managed on a single medical reference device 10. Contentis organized hierachically, usually by medical sub-specialty and drugcategory, providing the most efficient method for accessing medicalinformation. These content files may authored in HTML files andprocessed by an application script that converts the HTML content intohandheld database formats for viewing within the Reader 12.

[0017] In one example, the Reader 12 includes tabs or icons forselecting an index, a table of contents, and conversion equations for acontent file. Examples of content files 20 may include files forassisting physicians to diagnose illnesses or injuries. Others mayinclude files for drug information. In one example, a table of contentsfor the PEPID Portable Drug Companion is reproduced below:

[0018] PEPID PDC

[0019] Portable Drug Companion

[0020] Table of Contents

[0021] Drugs

[0022] Toxicology

[0023] Conversion Equations

[0024] About PEPID PDC

[0025] Warning

[0026] Drugs

[0027] Anesthesia

[0028] Cough & Cold Preparations

[0029] Dermatology

[0030] Eye/ENT

[0031] Gastrointestinal

[0032] Heart/Vascular

[0033] Vitamins & Minerals

[0034] Herbs & Food Supplements

[0035] Anti-Infectives

[0036] Metabolic & Endocrine

[0037] Hematology & Oncology

[0038] Neurological Agents/Psychiatry

[0039] Obstetrics & Gynecology

[0040] Pain

[0041] Immune Agents & Misc. Drugs

[0042] Vaccinations & Immunizations

[0043] Drug Interactions

[0044] Canadian Drug Trade Names

[0045] Toxicology

[0046] General

[0047] Toxin Identification

[0048] Poison Control Centers

[0049] Drugs of Abuse

[0050] Household Items

[0051] Plants

[0052] Inhaled Toxins

[0053] Hazardous Materials

[0054] Overdoses

[0055] Antidotes

[0056] Other

[0057] Conversion Equations

[0058] SI Units

[0059] Distance

[0060] Weight

[0061] Temperature

[0062] Pressure

[0063] Volume

[0064] Age Related Tables

[0065] Each of the entries in the table of contents may be linked tofurther information on the topic. For example, selecting “Anesthesia”links to the following information:

[0066] Anesthesia Drugs

[0067] Induction Agents

[0068] Premedication

[0069] General Anesth.

[0070] Paralysis

[0071] Miscellaneous

[0072] Induction Agents •Methohexital (Brevital)

[0073] Thiamylal (Surital)

[0074] Thiopental (Pentothal)

[0075] Premedication •Atropine (Atropine)

[0076] Glycopyrrolate (Robinul)

[0077] General Anesthetics •Desflurane (Suprane)

[0078] Etomidate (Amidate)

[0079] Ketamine (Ketalar)

[0080] Propofol (Diprivan)

[0081] Sevoflurane (Ultane)

[0082] Neuromuscular Blockers (Paralysis) •Neuromuscular Blockers DrugInteractions

[0083] Atracurium (Tracrium)

[0084] Botulinum Toxin (Botox, Myobloc)

[0085] Doxacurium (Numorax)

[0086] Mivacurium (Mivacron)

[0087] Pancuronium (Pavulon)

[0088] Rapacuronium (Raplon)

[0089] Rocuronium (Zemuron)

[0090] Succinylcholine (Anectine)

[0091] Vecuronium (Norcuron)

[0092] Misc. •DPT Combination DemerolVPhenergan/Thorazine

[0093] Selecting one of the listed drugs, Thiopental, for example, maylead to the following information:

[0094] [TOPICS][INRX]

[0095] Thiopental (Pentothal)

[0096] Dosing

[0097] Adult: •3-5 mg/kg IVP+/−infuision

[0098] Cerebral edema: 1.5-5 mg/kg IV ×1 dose

[0099] Anesthesia: •Induction: 2-6 mg/kg IV ×1 dose

[0100] Maint.: 50-100 mg IV PRN

[0101] Neurosurgical pts with incr ICP: 1.5-3.5 mg/kg IV with properventilatory support

[0102] Convulsive states: 75-125 mg IVP

[0103] Peds: •See adult dose; administration based on pt response

[0104] Deep sedation: 30 mg/kg PR ×1 dose ; NMT 1 g/dose

[0105] Dosage forms: [20 mg/mL, 25 mg/mL]; 800 mg/2 g rectal suspn

[0106] Indications

[0107] Depresses CNS to produce hypnosis, anesthesia & retrogradeamnesia WITHOUT analgesia

[0108] In high dose, may be used to reduce ICP, and depress cerebralmetabolism

[0109] C-Ind

[0110] Lack of ventilatory support, porphyria, hypotension

[0111] ADR's

[0112] Cardiovascular depression, hypotension, arrhythmias, arrest,laryngospasm, apnea, salivation

[0113] CAUTION: rapid bolus doses will increase cardio-respiratoryeffects: laryngospasm, apnea, hypotension, myocardial depression,cardiovascular collapse

[0114] Pregnancy Category: C

[0115] Kinetics

[0116] Hepatically conjugated to inactive metabolites, excreted inurine; 3-6 hr t1/2

[0117] Onset: 30-60 sec

[0118] Duration: 20-30min

[0119] Additive/synergistic effects if administered with or following anopioid, sedative or inhalational anesthetic agent

[0120] Slow release of this drug from lipoidal tissue result inprolonged anesthesia, somnolence, and respiratory and cardiovasculardepression

[0121] Mechanism of Action

[0122] Baribiturate; no musc. relaxant activity

[0123] Overdose Management

[0124] See Barbiturate OD

[0125] Interactions

[0126] Anesthetics: “incr thiopental” [anesthetics generally incr levelsor activity of thiopental]

[0127] Narcotics: incr thiopental

[0128] Phenothiazines: incr thiopental

[0129] Probenecid: incr thiopental

[0130] Sulfisoxazole: incr thiopental

[0131] Sedatives: incr thiopental

[0132] The dosage information may be linked to an integrated dosagecalculator 30 by one or more linking icons. Each linking icon may causethe Reader to pass different parameters to the dosage calculator 30 fora single drug. With respect to the above example for Thiopental,selecting Adult, Cerebral edema, Anesthesia, and Deep sedation wouldeach pass a different parameter to the dosage calculator.

[0133] In one example, the medical reference device 10 is secured viaapplication code, and a registration code is required in order to accessthe PEPID content files. The Document Manager Application DMA 14provides functionality for users to register, activate, access andmanage one or more PEPID content files for which they have subscribed orpurchased. The DMA 14 provides the ability to access this medical anddrug reference information as a result of a one-time purchase or atime-specific subscription period. Subscription periods can be set forany length of time, including an unlimited time period. Thissubscription period is used by the DMA 14 to control access to thecontent files 20 allowing access while in the subscription period, andrestricting access while outside of the subscription period.Additionally, the DMA 14 provides the ability to access content files 20during an automatically expiring trial period with no registration orsubscription information required.

[0134] The DMA 14 provides the ability to access and manage contentfiles in either a handheld device's primary memory or on detachableexpansion memory media, i.e. CF cards, SD cards, Memory Sticks, etc.,inserted into the device. In addition to handheld devices, the medicalreference application may be used on desktop or laptop computers, withfiles stored in disk drives or other suitable storage.

[0135] Content and application files may be delivered to users via oneof several delivery options, including electronic delivery over theinternet and CD ROM, and are ultimately installed to the end users'handheld devices via the synchronization method provided by their devicemanufacturer. Users have the ability to install the content files 20 tothe handheld device's main memory or to expansion memory. Users alsohave the ability to install content files 20 to a desktop or laptopcomputer.

[0136] Upon accessing the medical reference device 10 users are provideda list of content files 20 loaded on their device. For each content filelocated on the handheld device, users have the option to register thefile, open the file, delete the file, or copy the file to expansionmemory. In addition to content file-specific functionality, users havethe ability to remove all PEPID applications associated with the medicalreference application and content from the handheld device.

[0137] From the DMA 14, users are provided a variety of system messages.These messages vary depending upon several factors, including thecurrent state of the subscription and registration, including triggersfor when registration has not occurred, when the subscription is aboutto expire, and when the subscription has expired, and when system errorsare detected. Messages appear in two formats, either within the primaryDMA screen or within a pop-up dialog box.

[0138] Upon accessing a content file 20 via the DMA 14, users enter theReader (sending application) 12. Within the Reader 12, users may browsethrough content via icons and text-based links, either navigating toanother content card or launching a complementary application, such asone of the medical calculators 16, 30. Navigation features includeselecting icons or text-based links, moving back and forward along therecent navigation history, jumping to the top or bottom of the page,selecting from a dynamic navigation list to “quick jump” to sections onthe page, accessing the table of contents, and accessing a databasedriven index.

[0139] Within the Reader 12, users may create bookmarks to mark acontent location for later reference. Users may also copy any contentpage to a text file for printing or use in another electronicapplication.

[0140] 2 Handheld Medical Calculators

[0141] 2.1 Drug Dosing Calculator

[0142] The Drug Dosing Calculator 30 is application that enables usersto calculate weight-based, body-surface-area-based and age-based drugdosing amounts. The calculator is accessed via a link within an icon- ortext-based link 18 within a content page in the Reader 12. The link 18closes the Reader application 12 and launches the Drug Dosing Calculator30. All applicable parameters are passed between the two applications toenable true integration. FIG. 2 illustrates some examples of parameterstrings. The parameters may be dependent on a specific condition beingviewed in the Reader 12. For example, a dosage parameter for a givendrug may differ for different illnesses.

[0143] The Drug Dosing Calculator 30 accepts a parameter from the Reader12 identifying the appropriate drug for which a dosing calculation isdesired. Upon entering the Drug Dosing Calculator 30, the applicationdynamically determines if the drug dosing calculation is weight-based,body-surface-area-based, and/or age-based, prompting the user for theappropriate patient-specific value in several available units ofmeasure. For weight-based and surface area-based dosing calculations,the user has the option to calculate an estimate of the patient's weightor surface area, respectively. Upon entering or estimating the inputvalue, the calculator proceeds to calculate the appropriate drug dosingamount based on the inputs. The user is presented with the formula usedto calculate the dosing, the drug dosing amount in the applicablestandard unit, the frequency and duration of dosing, and conversionsinto liquid-based dosing for standard concentration formulas.Additionally, the calculator automatically checks that all input valuesfall within acceptable ranges and that the final recommended dosingfalls within acceptable minimum and maximum amounts.

[0144] 2.2 General Description of External Link Functionality

[0145] In one example of linking a Reader 12 to a calculator, externallinks 18 within the documents take the following form:

<a href=“protocol:creatorid.type?params”. . . >

[0146] where protocol = palm | palmcall creatorid = 4 character PalmOScreator id of the application to launch type = PalmOS type of theapplication to launch params = the parameter string

[0147] The use of the “palm” protocol indicates that the Reader 12should quit and launch the UI application specified. The use of the“palmcall” protocol indicates that the Reader 12 should launch thespecified application as a subroutine. In either case, the Reader 12.will launch the target application using the sysAppLanchCmdURLParamsPalmOS launch code. This launch code is accompanied by a parameter blockconsisting of the parameter string above.

[0148] 2.3 Unit Conversion Calculator

[0149] The Unit Conversion Calculator 16 is a complementary applicationthat enables users to calculate standard unit conversions for weight,distance, volume, temperature, and pressure. The Unit ConversionCalculator 16 accepts a parameter from the Reader 12 identifying theappropriate conversion category. Users enter a single input value forthe value to convert, select the applicable unconverted and convertedunits of measure, and calculate the converted value.

[0150] 2.4 US to SI Unit Conversion Calculator

[0151] The US to SI (Standard International) Unit Conversion Calculatoris a complementary application that enables users to quickly convertresults for various standard medical test results from the standardunits used in the United States to those units used internationally, andvice versa. The US to SI Unit Conversion Calculator accepts a parameterfrom the Reader identifying the appropriate test result to convert.Users enter a single input value, either the US or SI value, andcalculate the other. The Unit Conversion Calculator is linked in amanner similar to Conversion Calculator 16, and is not separatelyillustrated.

[0152] 2.5 Configurable Handheld Medical Calculator Application

[0153] The Configurable Handheld Medical Calculator Application 32 (FIG.3) is a complementary application that enables administrators of theapplication to define parameters for a medical calculation within an XMLdefinition, which are then converted into a handheld database andinterpreted within the Configurable Handheld Medical Calculatorapplication in order to produce an unlimited number of medicalcalculators.

[0154] Calculations that meet the following criteria can be configuredto function within the application without any programming required:

[0155] All input values are numeric, dates or lists where each item canbe converted to a numeric value.

[0156] Require at least one input value.

[0157] Results can be calculated via a mathematical formula, i.e. noconditional logic within the calculation.

[0158] The defined medical calculations are processed in an applicationthat enables users to enter multiple input values, enter values in avariety of units of measure, calculate a formulaic result, and validateall inputs and results against pre-defined minimum and maximum allowablevalues.

[0159] In one example Configurable Handheld Medical Calculatorsapplication consists of three parts:

[0160] A handheld application/GUI, which is integrated into the PEPIDDMA 14.

[0161] A Calculator Definition Database 34 containing the calculatordefinitions.

[0162] Calculator Look-up Tables 36 containing the lookup tables for anyand all calculators defined in Calculator Definition Database 34.

[0163] In addition, the application requires three files to be used togenerate the two databases above:

[0164] A script to generate databases

[0165] A Generic Calculator Document Type Definition (DTD)

[0166] An XML file containing calculator definitions (calculatordefinition file)

[0167] To generate the two databases above, users execute the script,which references the DTD and XML file to create the two requiredhandheld databases.

[0168] In the calculator definition database 34, users can define anunlimited number of medical or non-medical calculators. The calculatordefinition database 34 must conform to the Generic Calculator DTD. TheDTD specifies what XML elements (markup tags) are allowed, what XMLelements are required, and how the XML elements can be nested. The DTDalso specifies the attributes that may be provided for each element andwhat attributes may be omitted for each element. The basic structure forthe calculator definition file is as follows:

[0169] <?xml version=“1.0” encoding=UTF-8”?>

[0170] <!DOCTYPE gencalc SYSTEM “gencalc.dtd”>

[0171] <gencalc>

[0172] </gencalc>

[0173] Where one or more <calculator> elements are nested within the<gencalc> element for each calculator. Users must nest one calculatorelement within the <gencalc> element for each calculator. The syntax ofthe <calculator> element is shown below with required attributes initalics.

[0174] <calculator id=‘[4 character string]’ >

[0175] </calculator>

[0176] where the <calculator> element attributes are defined as follows:

[0177] id A 4-character ID that is unique amonge <calculator> elements.

[0178] Exactly one occurrence of each of the following elements must benested within the calculator element: <title>[text]</title>  [text] Thename of the calculator. <rpn>(text)</rpn>  (text) RPN equation. Seedetails below. <indexkeyword>[text]</indexkeyword>  [text] (Start of)the keyword to highlight when launching the Index.<shortcomment>[text]</shortcomment>  [text] Short comment to displaybelow the result field. <longcomment>[text]</longcomment>  [text] Longcomment to appear in the popup comment form. <result>[childelements]</result>

[0179] see details below.

[0180] In addition, one or more occurrences of the following elementsmust be nested within the calculator element:

[0181] <input>[child elements]</input>

[0182] See details below.

[0183] In one example, users must nest one and only one <rpn> elementwithin each calculator element:

[0184] <rpn>(text)</rpn>

[0185] Where (text) is an equation specified in reverse polish notationthat contains variables, operators, and numeric values.

[0186] Allowed Variables:

[0187] [a, p] where each character is mapped to the<input> element whose‘var’ attribute value is equal to the character, allowing a maximum of16 variables/inputs.

[0188] Allowed Operators:

[0189] +, −, *, and {circumflex over ( )}, which specify addition,subtraction, multiplication, division, and exponentiation, respectively.

EXAMPLE 1

[0190] You have four inputs (a, b, c, d), which are to be used in thefollowing equation specified in infix notation: (a+b)/(1 −(c+d)). Theappropriate <rpn> element definition would be:

[0191] <rpn>a b+1 c d+−/</rpn>

EXAMPLE 2

[0192] You have four inputs (a, b, c, d), which are to be used in thefollowing equation specified in infix notation: (a {circumflex over( )}b) +(c •d). The appropriate <rpn> element definition would be:

[0193] <rpn>a b{circumflex over ( )}c d*+</rpn>

[0194] Users must nest one and only one <result> element within eachcalculator element. The syntax of the <result> element is shown belowwith required attributes in italics.

[0195] <result name=‘[text]’>

[0196] </result>

[0197] where the<result> element attributes are defined as follows:

[0198] name The displayed name/label of the result.

[0199] The first child element nested within the <result> elementspecifies what to do with the numeric result computed by the RPNequation. Valid child elements are shown below with required attributesin italics.

[0200] <int min=‘. . .’ max=‘. . .’ default=‘. . .’ />

[0201] Format the computed result as an integer.

[0202] <float min=‘. . .’ max=‘. . .’ sigdigits=‘. . .’ default=‘. . .’/>

[0203] Format the computed result as an floating point number.

[0204] <date/>

[0205] Format the computed result as a date.

[0206] <lookup>

[0207] <interval. . ./>

[0208] </lookup>

[0209] Look up the computed result in the associated lookup tables.Lookup tables are defined by nesting one or more <interval> elements.

[0210] The attributes shown for the tags above are interpreted asfollows:

[0211] default Ignored/unused.

[0212] min: Minimum allowed value (empty value=negative infinity).

[0213] max: Maximum allowed value (empty value=positive infinity).

[0214] sigdigits Number of significant digits to use when formatting theresult. The default number of significant digits is 4.

[0215] Each <interval> element nested within a <lookup> elementspecifies a lookup interval. The syntax of the <interval> element isshow below with required attributes in italics.

[0216] <interval min=‘[numeric]’ max=‘[numeric]’ value=‘[string]’/>

[0217] Where the attributes for the <interval> element are interpretedas follows:

[0218] min: Minimum interval value (empty value=negative infinity).

[0219] max: Maximum allowed value (empty value=positive infinity).

[0220] value The value to display if the result falls within theinterval [min, max].

[0221] If the first child element is an<int>, <float>, or<date> element,then you may also nest a single <staticunit> or <dynamicunit> elementwithin the <result> element. If the first child element is a <lookup>element, then you may also nest a single <staticunit> element within the<result> element.

[0222] Users must nest one <input> element within each <calculator>element for each of the calculator input values. The syntax of the<input > element is shown below with required attributes in italics.

[0223] <input name=‘[text]’ var=‘[single character]’ >

[0224] </input>

[0225] where the <input> element attributes are defined as follows: nameThe displayed name/label of the input. var The associated input variablethat appears in the RPN equation that is unique among <inputs> elementswithin each <calculator> element.

[0226] The first child element nested within the <input> elementspecifies the type of the input to be entered by the user. The validchild elements are shown below with required attributes in italics:

[0227] <int min=‘. . .’ max=‘. . .’ default=‘. . .’ />

[0228] The input must be an integer value.

[0229] <float min=‘. . .’ max=‘. . .’ sigdigits=‘. . .’ defautl‘. . .’/>

[0230] The input must be a floating point value. <date/>

[0231] The input is a date.

[0232] enum default=‘[integer]’ >

[0233] <option. . ./>

[0234] </enum>

[0235] The input is an enumeration (popup list). Options in the popuplist are defined by nesting one or more <option> elements.

[0236] The attributes shown for the tags above are interpreted asfollows:

[0237] min: Minimum allowed value (empty string=negative infinity).

[0238] max: Maximum allowed value (empty string=positive infinity).

[0239] sigdigits Number of significant digits to use when formatting theresults of conversions between values. The default number of significantdigits is 4.

[0240] default For <int> and <float>, this is the default value to bedisplayed.

[0241] For <enum>, this is the default option to select. Each <option>element nested within an <enum> element specifies an option in the popuplist. The syntax of the <option> element is show below with requiredattributes in italics.

[0242] <option value=‘. . .’ label=‘. . .’/>

[0243] where the attributes for the <option> element are interpreted asfollows: value The value to use in the RPN equation when this option isselected. label The associated text to display in the popup list.

[0244] If the first child element is an <int>, <float>, or <date>element, then you may also nest a single <staticunit> or <dynamicunit>element within the <input> element. If the first child element is an<enum> element, then you may also nest a single <staticunit> elementwithin the <input> element. See “Unit Definitions” below for moredetails.

[0245] Subject to the restrictions noted above for <result> and <input>elements, input and result units may be specified as simple strings oras a list of options in a ‘unit popup list’. Simple unit strings arespecified as follows:

[0246] <staticunit>[text]</staticunit>

[0247] Unit popup lists are specified using the <dynamicunit> elementwhich contains one or more nested <option> units. The syntax of the<dynamicunit> element is show below with required attributes in italics.<dynamicunit default=‘[integer]’>  <option value=‘[factor]’label=‘[text]’ />  ... </dynamicunit>

[0248] where the attributes for the <dynamic > element are defined asfollows:

[0249] default The default selected unit.

[0250] and the attributes for the <option> element are interpreted asfollows:

[0251] label The text displayed in the unit popup list.

[0252] value The multiplicative factor applied to each associated valuebefore using the value in the rpn equation (for inputs):

input to RPN equation=user_input* [factor]

[0253] converting between values when the user selects a new unit fromthe unit popup list (for both inputs and results):

converted value=user_input* [new factor]/[current factor]

EXAMPLE 1

[0254] Your RPN equation requires an input in centimeters. You want toallow the user to enter the input value in millimeters, centimeters, ormeters. Given the following:

[0255] Base unit: cm

[0256] 1 cm=10 mm

[0257] 1 cm=0.01 m

[0258] The appropriate dynamic unit definition would be: <dynamicunit> <option value=‘10’ label=‘mm’ />  <option value=‘1’ label=‘cm’ /> <option value=‘0.01’ label=‘m’ /> </dynamicunit>

EXAMPLE 2

[0259] Your RPN equation calculates a result in centimeters. You want tobe able to display the unit in centimeters or inches. Given thefollowing:

[0260] Base unit: cm

[0261] cm=0.39 in

[0262] The appropriate dynamic unit definition would be: <dynamicunit> <option value=‘1’ label=‘cm’ />  <option value=‘0.39’ label=‘in’ /></dynamicunit>

[0263] 3 Handheld Drug Interactions Reference

[0264] The handheld Drug Interactions Reference is a complementaryapplication that enables users to quickly assess the interaction effectsof a list of new drugs (subject drugs) against a list of currentlyprescribed drugs (object drugs). The application accepts one to manyparameters from the Reader 12, denoting any drugs selected topre-populate the drug list.

[0265] The Drug Interactions Reference application 40 evaluatespotential interactions based on each drug's pharmacokinetic,pharmacodynamic, and other characteristics. When the characteristics of2 drugs taken together suggest a possible interaction then the possibleinteraction, its mechanism and potential severity are presented. Allresults can be overridden when actual studies suggest a differentinteraction. The application can also attribute characteristics toentire classes and groups of drugs.

[0266] Upon entering the application from the Reader 12, users areprompted to select a list of drugs that contains all subject and objectdrugs from a quick-search index that allows multiple selections andquick navigation through the drug list as each letter of the drug isspelled out.

[0267] After the entire drug list is identified, the user selects withdrugs are the subject drugs, i.e. “new” drugs in the patient's drugtreatment regimen, and which drugs are object drugs, i.e. “existing”drugs in the patient's drug treatment regimen. To assess the variousdrug interactions, the application evaluates drug pairs, evaluating eachsubject drug against each other subject drug and each object drug.

[0268] Interactions are presented on a summary screen with abbreviatednames, icons and interaction codes, and on a detail result screen wherea full-text description of each interaction appears.

What is claimed is
 1. A medical reference device comprising: a. ageneral purpose computer; b. the general purpose computer configuredwith:
 1. a plurality of medical and drug information content pages;
 2. areader application, the reader application configured to display medicaland drug information content pages and to generate a plurality ofparameter strings in response to user-selected medical and druginformation;
 3. a drug dosing calculator application configured toreceive at least one of the parameter strings generated by the readerapplication and to return dosing information to the reader application.2. The medical reference device of claim 1, wherein the general purposecomputer comprises a portable handheld computer.
 3. The medicalreference device of claim 2, wherein the portable handheld computercomprises a Palm OS device.
 4. The medical reference device of claim 2,wherein the portable handheld computer comprises a Windows OS device. 5.The medical reference device of claim 1, further comprising a documentmanager application, configured to receive at least one of the pluralityof parameter strings generated by the reader application and to providemedical and drug information content pages to the reader application. 6.The medical reference device of claim 5, wherein the document managerapplication further comprises a generic calculator, and wherein thedocument manager application is linked to a calculator definitiondatabase and calculator look up tables to provide calculator definitionsto the generic calculator.
 7. The medical reference device of claim 1,wherein the parameter string sent from the reader application to thedrug dosing calculator application includes drug dosing parameterscorresponding to a user-selected medical condition and a user-selecteddrug.
 8. The medical reference device of claim 1, wherein the parameterstring sent from the reader application to the drug dosing calculatorapplication includes drug dosing parameters corresponding to medical anddrug information included on a selected medical and drug informationcontent page.
 9. The medical reference device of claim 1, wherein theparameter string sent from the reader application to the drug dosingcalculator application comprises a plurality of parameter strings.
 10. Amedical reference device comprising: a. a general purpose computer; b.the general purpose computer configured with:
 1. a plurality of medicaland drug information content pages;
 2. a reader application, the readerapplication configured to display medical and drug information contentpages and to generate a plurality of parameter strings in response touser-selected medical and drug information;
 3. a document managerapplication, configured to receive the plurality of parameter stringsgenerated by the reader application and to provide medical and druginformation content pages to the reader application.
 11. The medicalreference device of claim 10, wherein the document manager applicationis configured to manage an integrated medical and drug informationdatabase, including updating and controlling access to medical and druginformation content pages.
 12. The medical reference device of claim 10,wherein the document manager application is configured to allow accessto medical drug information content pages during the time period of auser subscription.
 13. The medical reference device of claim 10, whereinthe document manager application further comprises a generic calculator,and wherein the document manager application is linked to a calculatordefinition database and calculator look up tables to provide calculatordefinitions to the generic calculator.
 14. A medical reference devicecomprising: a. a general purpose handheld computer; b. the generalpurpose handheld computer configured with:
 1. a plurality of medical anddrug information content pages;
 2. a reader application, the readerapplication configured display medical and drug information contentpages and to generate a plurality of parameter strings in response touser-selected medical and drug information;
 3. a document managerapplication, configured to receive the plurality of parameter stringsgenerated by the reader application and to provide medical and druginformation content pages to the reader application, wherein thedocument manager application further comprises a generic calculator, andwherein the document manager application is linked to a calculatordefinition database and calculator lookup tables to provide calculatordefinitions to the generic calculator;
 4. a drug dosing calculatorapplication configured to receive at least one of the parameter stringsgenerated by the reader application and to return dosing information tothe reader application; and
 5. a unit conversion calculator configuredto receive at least one of the parameter strings generated by the readerapplication and to return converted units to the reader application. 15.The medical reference device of claim 14, wherein at least one of theplurality of parameter strings includes drug dosing parameterscorresponding to medical and drug information included on a selectedmedical and drug information content page.
 16. The medical referencedevice of claim 14, wherein the parameter string sent from the readerapplication to the drug dosing calculator application includes drugdosing parameters corresponding to a user-selected medical condition anda user-selected drug.
 17. A method for calculating drug dosing using amedical reference device, comprising: a. configuring the computingdevice with medical and drug information content pages and a drug dosingcalculator; b. displaying at least one medical and drug informationcontent page on the computing device; c. selecting a medical conditionfrom a plurality of medical conditions displayed on the computing devicebased on observations of a patient and displayed medical information; e.selecting a drug from a plurality of drugs displayed on the computingdevice; f. passing drug dosing parameters corresponding to the selectedmedical condition and the selected drug to the drug dosing calculator;and g. displaying a calculated drug dose.
 18. The method of claim 17,further comprising the step of selecting a method of administering theselected drug and wherein the drug dosing parameters further includesparameters corresponding to the selected method of administering thedrug.